In the 1970s, Bang, Dyerberg and Nielsen described the plasma lipid and lipoprotein pattern of Eskimos living on the west coast of Greenland, and compared it with that of the Danish population (H. O. Bang, J. Dyerberg and A. B. Nielsen. Plasma lipid and lipoprotein pattern in Greenlandic West-coast Eskimos. Lancet 1971; 1:1143-45). Later, Dyerberg and his collaborators (J. Dyerberg, H. O. Bang and N. Hjørne. Fatty acid composition of the plasma lipids in Greenland Eskimos. American Journal of Clinical Nutrition 1975; 28:958-66) related the differences they found, to the remarkably low mortality from coronary heart disease among the Eskimos, compared to Danes. Since the dietary fat intake was almost the same in the two populations, they suggested that the striking difference in coronary heart disease could be due to the big difference in the intake of marine fats and that coronary heart disease could be associated with the chemical nature of the dietary lipids (J. Dyerberg, H. O. Bang. E. Storffersen, S. Moncada and J. R. Vane. Eicosapentaenoic acid and prevention of thrombosis and atherosclerosis? Lancet 1978; 2:117-19). After these pioneering studies, it became evident that coronary heart disease, which is still among the most serious killer diseases in Western societies, could no longer be regarded merely as a lipid storage disease caused by excessive dietary fat intake.
The scientists who pioneered this research were the first to suggest that the anti-atherogenic factors in the traditional Eskimo diet were marine long chain poly unsaturated fatty acids (PUFAs). Their diet, consisting largely of seal, whale and seabirds, and, to some extent, fish, provided several grams—may be as much as 15 grams—of such fatty acids each day. This is far more than a typical “modern” Western diet contains.
Research during the last 30-40 years has confirmed the classical studies by the Dyerberg group and established a firm scientific foundation for a common understanding among scientists and other professionals: The health benefits of sea-food and marine oils can first and foremost be associated with two typical marine PUFAs, namely eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). This statement is in line with the conclusions and recommendations from the symposium “Beyond Cholesterol: Prevention and Treatment of Coronary Heart Disease with n-3 Fatty Acids, published by Deckelbaum et al. (American Journal of Clinical Nutrition 2008; 87(suppl): 2010S-2S).
EPA and DHA contain, respectively, 20 and 22 carbon atoms with 5 and 6 conjugated double bonds, of which the first one is in the position 3 carbon atoms (n-3) counted from the hydrophobic (methyl) end of both these fatty acids. The abbreviation C20:5n-3 is often used as a chemical designation for EPA and C22:6n-3 for DHA. Phytoplankton in the marine environment is the primary producers of EPA and DHA, which follow the food-web from this first trophic level via zooplankton to fish and sea-mammals. Plant food oils and animal fat contain low levels, if any, of EPA and DHA.
EPA and DHA are believed to be particularly important in prevention of cardiovascular disease. Even modest sea-food intake, supplying 250 mg of EPA and DHA daily, seems sufficient to reduce the risk of coronary death by 36% and to reduce mortality in the general population by 17% (U. J. Jung et al. American Journal of Clinical Nutrition 2008; 87(suppl): 2003S-9S).
Physiological and molecular mechanisms proposed to explain the cardioprotective effects of EPA and DHA, include 1) lowering the levels of triacylglycerol and free fatty acids in plasma, 2) increasing high density lipoprotein (HDL) levels and decreasing low density lipoproteins (LDL) levels, 3) decreasing platelet aggregation, 4) decreasing cholesterol delivery and cholesterol deposition in arterial walls, 5) decreasing arterial inflammation. These are interactive mechanisms involving complex and diverse biochemical mechanisms, including effects of EPA and DHA as well as of their transformation products (prostaglandins, prostacycline, thromboxans, leukotrienes) on modulation of immunity and inflammation and gene expression in different cells and tissues. Although the health benefits of EPA and DHA no longer can be questioned, the mechanisms involved are too complex to be fully understood. For instance, it is still a puzzling fact that “the major mechanisms underlying the beneficial effects of n-3 fatty acids in the prevention and treatment of coronary artery disease appears to be distinct from effects on lowering plasma triacylglycerol concentrations” (Deckelbaum et al., American Journal of Clinical Nutrition 2008; 87(suppl): 2010S-2S).
Preclinical and human clinical studies during the last 30-40 years have provided consistent evidence that consumption of sea-food and marine food oils is beneficial for the health, and it has become generally accepted among those skilled in the art that these health benefits are, first and foremost, associated with EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). The total evidence related to the ability of these two marine n-3 PUFAs to prevent coronary heart disease is so overwhelming that it has become part of a primary prevention strategy of health authorities in Western societies to recommend daily EPA and DHA consumption. In support of this strategy, it can be referred to the symposium “Beyond Cholesterol: Prevention and Treatment of Coronary Heart Disease with n-3 Fatty Acids” summarized and discussed by R. J. Deckelbaum et al. (American Journal of Clinical Nutrition, 2008; 87 (suppl): 2010S-2S). Moreover, concentrates of EPA and DHA, produced as disclosed in U.S. Pat. Nos. 5,502,077, 5,656,667 and 5,698,594, have been approved by the US Food and Drug Administration (FDA) as pharmaceutical preparations that reduce the level of blood components regarded as risk factors for coronary heart disease.